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<h1 id="h5新增的标签有什么，为什么要加强语义化"><a href="#h5新增的标签有什么，为什么要加强语义化" class="headerlink" title="h5新增的标签有什么，为什么要加强语义化"></a>h5新增的标签有什么，为什么要加强语义化</h1><p>html5增加了<code>&lt;main&gt;&lt;header&gt;&lt;footer&gt;&lt;aside&gt;&lt;section&gt;&lt;video&gt;&lt;audio&gt;&lt;time&gt;&lt;data&gt;</code>之类的语义化标签, 搜索引擎会利用爬虫分析抓取页面结构内容，<code>有利于SEO，页面结构更加清晰，利于维护.提高页面可访问性，不会在样式加载不正常的时候一团乱，维持基本结构。利于部分残障人士页面阅读器解析</code></p>
<h1 id="为什么要清除浮动，如何清除浮动"><a href="#为什么要清除浮动，如何清除浮动" class="headerlink" title="为什么要清除浮动，如何清除浮动"></a>为什么要清除浮动，如何清除浮动</h1><ol>
<li>浮动脱离了正常文档流,会导致父元素高度塌陷，后面元素会挤到浮动元素下方，造成布局错乱。</li>
<li>清除浮动：</li>
</ol>
<ul>
<li>为父元素创建BFC（块级格式化上下文，是一个独立渲染的区域），即添加一个<code>overflow:hidden;</code>。也不推荐，因为会造成一些副作用</li>
<li>在最后一个浮动元素后面添加一个标签，其属性为：<code>clear：both；</code>。但是这种做法不推荐，增加了额外的标签，语义化差</li>
<li>使用after伪元素清除浮动（推荐）<figure class="highlight css"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="selector-class">.clearfix</span><span class="selector-pseudo">:after</span>&#123;<span class="comment">/*伪元素是行内元素 正常浏览器清除浮动方法*/</span></span><br><span class="line"><span class="attribute">content</span>: <span class="string">""</span>;</span><br><span class="line"><span class="attribute">display</span>: block;</span><br><span class="line"><span class="attribute">height</span>: <span class="number">0</span>;</span><br><span class="line"><span class="attribute">clear</span>:both;</span><br><span class="line"><span class="attribute">visibility</span>: hidden;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

</li>
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<h1 id="行内元素和块级元素雨哦哪儿些，他们有什么不同"><a href="#行内元素和块级元素雨哦哪儿些，他们有什么不同" class="headerlink" title="行内元素和块级元素雨哦哪儿些，他们有什么不同"></a>行内元素和块级元素雨哦哪儿些，他们有什么不同</h1><ul>
<li>行元素无法设置宽高,行排布,不够换行 a b span img input button label</li>
<li>块元素独占一行,可以设置宽高 p div ul ol form table </li>
<li>还有空元素:link br hr等</li>
</ul>
<h1 id="有什么存储数据的方式，有什么不同"><a href="#有什么存储数据的方式，有什么不同" class="headerlink" title="有什么存储数据的方式，有什么不同"></a>有什么存储数据的方式，有什么不同</h1><ul>
<li>cookie sessionStorage localStorage indexDb</li>
<li>cookie按设定的时间内有效，最多4k</li>
<li>两个storage都是html5新api,存储键值对,sessionStorage会话存储,页面访问时间内有效，关闭页面失效,localStorage一直有效，关闭页面不会失效，两个都是最大5M</li>
<li>indexdb也是h5新api，浏览器内置小型数据库。</li>
</ul>
<h1 id="vue实现双向绑定的原理"><a href="#vue实现双向绑定的原理" class="headerlink" title="vue实现双向绑定的原理"></a>vue实现双向绑定的原理</h1><p>原理就是通过<code>‘数据劫持’ + 订阅发布模式实现</code></p>
<h2 id="数据劫持"><a href="#数据劫持" class="headerlink" title="数据劫持"></a>数据劫持</h2><p>指的是在访问或者修改对象的某个属性时，通过一段代码拦截这个行为，进行额外的操作或者修改返回结果</p>
<p>典型的有<br>1.Object.defineProperty()<br>2.es6中Proxy对象</p>
<p>vue2.x使用Object.defineProperty();<br>vue3.x使用Proxy;</p>
<h2 id="订阅发布者模式"><a href="#订阅发布者模式" class="headerlink" title="订阅发布者模式"></a>订阅发布者模式</h2><p>定义：<code>对象间的一种一对多的依赖关系，当一个对象的状态发生改变时，所有依赖于它的对象都将得到通知</code></p>
<h1 id="怎么实现文本不自动换行，超出文本的部分变成省略号"><a href="#怎么实现文本不自动换行，超出文本的部分变成省略号" class="headerlink" title="怎么实现文本不自动换行，超出文本的部分变成省略号"></a>怎么实现文本不自动换行，超出文本的部分变成省略号</h1><figure class="highlight css"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="selector-tag">white-space</span><span class="selector-pseudo">:nowrap</span>; </span><br><span class="line"><span class="selector-tag">overflow</span><span class="selector-pseudo">:hidden</span>;</span><br><span class="line"><span class="selector-tag">text-overflow</span><span class="selector-pseudo">:ellipsis</span>;</span><br></pre></td></tr></table></figure>

<h1 id="vue的生命周期有哪些，分别有什么不同"><a href="#vue的生命周期有哪些，分别有什么不同" class="headerlink" title="vue的生命周期有哪些，分别有什么不同"></a>vue的生命周期有哪些，分别有什么不同</h1><p>看官网的图</p>
<h1 id="跨域的原理有哪些，jsonp的原理是什么？"><a href="#跨域的原理有哪些，jsonp的原理是什么？" class="headerlink" title="跨域的原理有哪些，jsonp的原理是什么？"></a>跨域的原理有哪些，jsonp的原理是什么？</h1><ul>
<li>跨域浏览器安全策略造成，非同协议，源，端口　皆为跨域，为了避免csrf跨域请求伪造，请求会被浏览器拦截。</li>
<li>实现跨域请求:jsonp ,后端设置CORS, 各种代理 像nginx,node中间件。跨域访问dom:Window.postMessage, document.domain,iframe</li>
<li>jsonp原理:利用script不受同源政策限制,将请求模拟成script标签请求,写入callback回调函数，后台将结果用callback包装返回，回调函数即可得到数据，，不过jsonp只支持get请求</li>
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